Aldosterone is the major mineralocorticoid hormone that regulates sodium (Na) homeostasis and its action contributes to the maintenance of blood pressure and cardiac function. Abnormal aldosterone signaling can lead to hypertension, a syndrome that affects at least 25% of American adults. Hypertension is a primary risk factor for cardiovascular disease, the leading cause of death in the United States. Most known monogenetic causes of hypertension are due to a defect in the downstream targets of aldosterone action. The mechanism of aldosterone action is largely transcriptional with most known gene targets converging on the renal epithelial sodium channel (ENaC). Recent data suggest a role for the aldosterone target Period 1, a circadian rhythm gene, in mediating the aldosterone-dependent and independent regulation of the alpha subunit of ENaC ((ENaC), the rate limiting subunit for the Na channel in the kidney. Many physiological processes exhibit a circadian pattern, including the sleep-wake cycle, heart beat, hormone secretion, renal blood flow, and blood pressure. However, the role of the circadian clock in the regulation of these processes is not understood at a molecular level. The long term goal of these studies is to characterize the role of the circadian clock in hypertension and cardiovascular disease. The goal of the present application is to define a functional role for Per1 in the regulation of (ENaC. To this end, the aims of this proposal are to (1) characterize the Per1-mediated transcriptional regulation of the (ENaC gene, (2) define the role of Per1 in the regulation of ENaC activity, and (3) evaluate the role of Per1 in the regulation of (ENaC in vivo. Evidence of a direct molecular and physiological link between ENaC and the circadian clock is likely to have profound implications for understanding renal Na handling and possibly blood pressure control in pathophysiological conditions. The candidate will use the work described in this proposal as the basis for developing an independent line of research into circadian and aldosterone-mediated control of Na transport in the kidney. Thus, a comprehensive training program has been designed to move the applicant to a career as an independent investigator. Didactic coursework, seminars and journal clubs will provide the candidate with new and formal training in physiology as well as additional training in renal physiology and the responsible conduct of research. Dr. Charles Wingo, a highly regarded nephrologist and expert in renal ion transport, will serve as the candidate's mentor. An Advisory Committee has been assembled to aid the candidate in scientific and career development. Drs. Charles Wingo, Mark Segal, Julie Johnson, Barbara Battelle and Douglas Eaton are experts in the fields of nephrology, physiology, pharmacology, and neuroscience. The outstanding environment of the University of Florida, rich in clinical and basic sciences, together with the scientific plan and comprehensive training program, will offer the candidate the best opportunity for achieving her goal of becoming an independent investigator in the field of renal physiology.